Recently, I used chipe AD549 to for a I/V converter to amplifier the pA current. But I found the Ibs of AD549 is more than 20pA, which is very different with 50fA that is discribed in its datasheet. This result I get from NI Multism simulation.
So I feel very curious weather there is something wrong in my circuit or AD549 is oringinally not suitable for ultra current amplifer. Looking forward to your kind hlep.